Group B streptococcal disease is a major cause of morbidity and mortality in the newborn. Antibiotic therapy has proven relatively ineffective in controlling or preventing the disease. One promising approach is vaccination of pregnant women against group B streptococcal antigens in order to induce a protective transplacental antibody response. As yet, there is no acceptable experimental model for evaluating potential group B streptococcal vaccines. By using a pregnant rabbit model, I will determine (1) if maternal immunization will induce protective antibody in the neonate, (2) which group B streptococcal antigens are most effective in generating that response, and (3) the efficacy of passive maternal immunization with antibody of limited specifity.